It is known in the arts pertaining to fluid flow in enclosed flow paths and around solid bodies that significant flow efficiencies can be obtained by he proper configuration of curving wall portions to conserve flow energy and avoid unnecessary sudden changes in pressure and flow direction. For example, it has long been recognized in regard to complex internal flow passages, such as piston engine ports and manifolds, the vaneless scroll collectors of radial flow turbomachinery and jet engine ducting, that continuous and smooth flow-area distributions and gradual boundary transistions between adjacent sections must be provided in order to minimize total pressure losses.
It has also been shown in my prior U.S. Pat. No. 3,860,360, granted Jan. 14, 1975 to the assignee of the present invention, that a super-elliptical equation may be utilized to define the boundaries of a diffuser duct for a centrifugal compressor having a flow path changing from rectangular to elliptical cross section over its length. However, the prior disclosure does not indicate any suitable manner of defining complex curved flow paths or straight paths of smooth and continuously varying cross-sectional shape and configuration except for the particular embodiment disclosed in my prior patent.